(1) Field of the Invention
The present invention relates to measuring the contour of a surface from a position located remotely from that surface and particularly to determining the profile of the surface of charge material which has been deposited on the hearth of a furnace. More specifically, this invention is directed to apparatus which employs a beam of energy, particularly electromagnetic energy, to determine the profile of the surface of the burden in a shaft furnace. Accordingly, the general objects of the present invention are to provide novel and improved methods and apparatus of such character.
(2) Description of the Prior Art
It is well known that proper exercise and control over the profile of the charge on the hearth of a blast furnace is essential to maximizing the efficiency of operation of the furnace. Obviously, in order to control charge profile, means must be provided for determining the contour of the surface of the charge at least on a periodic basis during the furnace charging operation. Devices for making such measurements are known in the art as profilometers. The prior art profilometers may be classified generally as either being of the mechanical probe type or the radiant energy type. The early mechanical probe type profilometers were capable of making a measurement at only a single point. Improved mechanical probe type profilometers enable the shifting of that single point of contact with the surface of the charge. This shifting of the measuring point, however, is accompanied by mechanical complexity and, for sufficient information to be collected so as to enable the charge profile to be determined, a large number of individual measurements are required thus making the task of determining the charge profile a time consuming endeavor. Examples of mechanical probe type profilometers of modern design may be found in U.S. Pat. Nos. 3,905,239 and 4,094,494. The profilometer of U.S. Pat. No. 4,094,494 is designed for use with a furnace charging installation of the type which is known in the art as a "bell-less top" or a "coneless throat." Such a charging installation is shown and described in U.S. Pat. No. 3,693,812 and has the advantage of allowing exercise of a high degree of control over the charge profile when sufficient surface contour information is available.
Profilometers of the radiant energy type may be based upon radar technology and include means for transmitting electromagnetic energy to the charge surface and receiving energy reflected from the charge surface. A radar type probe is described in Luxembourg Pat. No. 70310. The profilometers which employ a beam of radiant energy constitute a technical advance over mechanical probes since they provide the requisite surface contour information rapidly and are particularly suitable for automatic control. This automatic control may, for example, result in the profile of the charging surface being measured on a periodic basis such as, for example, each time a layer of material has been deposited on the furnace hearth. Alternatively, the surface contour may automatically, with a radiant energy type profilometer, be measured in accordance with a predetermined program. In either case, the information derived by the profilometer may be employed to control the motion of the charge distribution chute of a furnace charging installation of the type shown in U.S. Pat. No. 3,693,812.
Profilometers of the radiant energy type, and particularly those which operate on the principle of radar, offer theoretical advantages when compared to profilometers of the mechanical probe type. However, because of the existence of a number of inherent problems, radar profilometers have not previously gained acceptance for use in commercial installations.
One of the problems alluded to above resides in the necessity of providing for the removal of the portions of the profilometer which are installed in the furnace, for maintenance by way of example, without impeding the operation of the furnace. In this regard, it should be noted that modern blast furnaces operate with high pressures and thus the problem of providing a hermetic seal is greatly complicated. The problem being discussed is further complicated by the fact that the beam of energy emitted from the probe must be caused to scan the surface of the charge on the furnace hearth, at least along a line, and this is accomplished by imparting motion to the antenna which transmits the energy and receives reflections from the surface of interest. The antenna will typically be of the parabolic type and, in order to permit passage of the antenna and the means by which it is scanned, the opening required in the furnace wall must be comparatively large. The problem thus becomes one of transmitting motion through the furnace wall, or an extension thereof which houses the antenna, without leakage of the pressurized furnace gases and without requiring shut-down of the furnace.
A second problem resides in maintaining the probe in operating condition. The conditions within the furnace constitute an exceedingly harsh operating environment and, during the charging process, the furnace atmosphere become laden with particulate matter. As a result, a deposit of dust rapidly forms on the parabolic reflector of the radar probe and, after but a few days of exposure to the furnace environment, the probe will become inoperable.